NAME
Exporter::Renaming - Allow renaming of symbols on import
SYNOPSIS
# Enable renaming in Exporter
use Exporter::Renaming;
# Import File::Find::find as main::search
use File::Find Renaming => [ find => search];
# Disable renaming
no Exporter::Renaming
ABSTRACT
Allow Renaming of symbols on Import
DESCRIPTION
Overview
This module adds the ability to rename symbols to the standard Exporter
module. After "use Exporter::Renaming", you can import symbols from
exporting modules not only under their original names, but also under
names of your choosing.
Here, *symbol* is used to mean anything that could be exported by a
Module, that is, a Perl function or variable. Thus a symbol begins with
an optional *type character* (one of "$", "@", "%", "&", and "*"),
followed by a name (a Perl identifier, made up of alphanumerics and "_",
starting with a non-digit).
To trigger renaming behavior, the import list of a subsequent "use
" statement must begin with the keyword 'Renaming', followed by
a list reference, the , which describes
the renaming imports (see below). After that, a normal import list may
follow, which Exporter processes as usual.
Renaming List
The renaming list contains *renaming pairs*, which are pairs of symbols.
The first part of a pair is the original symbol (as known to the
exporting module) and the second one is the renamed symbol (as you want
to use it after import). It is an error (fatal, as all "Renaming" or
"Exporter" errors) if the renaming list has an odd number of elements,
or if one of its symbols is invalid.
If none of the symbols in a *renaming pair* contains a *type character*,
an "&" is assumed. If only one has a *type character*, this type is
assumed for the other one too. If both have type characters, it is an
error if they don't agree.
If the renamed symbol (the second part) of a *renaming pair* is
undefined, the original symbol is imported unchanged, so you can include
normal imports in a renaming list without retyping the name.
It is an error for a symbol to appear more than once as the second part
of a *renaming pair*, that is, to specify the same thing twice as the
target of a renaming operation. It is allowed to import the same symbol
multiple times with different targets. Maybe it even makes sense in some
situations.
Operation
Exporter continues to behave normally for normal imports while renaming
behavior is switched on. Only the presence of the keyword "Renaming",
followed by an array reference in the first and second positions after a
"use" statement triggers renaming.
The renaming behavior of Exporter is thus compatible with its standard
behavior. If renaming must be switched off for some reason, this can be
done via "no Export::Renaming".
If an *import list* contains both a renaming list and a sequence of
normal import statements, the renaming is done first, as indicated by
its position. No cross-check is done between the results of renaming and
the normal imports, as if these resulted from two separate "use"
statements.
EXAMPLES
All examples assume that
use Exporter::Renaming;
has been called (and that "no Exporter::Renaming" hasn't).
The most obvious application of "Exporter::Renaming" is to solve a name
conflict. Suppose our module already defines a function "find", and we
want to use the standard "File::Find" module. We could then rename
"find" from "File::Find" to "search" in our own module:
use File::Find Renaming => [ find => 'search' ];
Let's assume the "finddepth" function from File::Find doesn't cause a
name conflict, and we want to import it under its original name as well.
This does it in the renaming list:
use File::Find Renaming => [
find => 'search',
finddepth => undef,
];
...as does this, but explicitly:
use File::Find Renaming => [
find => 'search',
finddepth => 'finddepth',
];
...while this uses a regular import:
use File::Find Renaming => [ find => 'search' ], 'finddepth';
Should you find it annoying that a pedantic module author has chosen to
adorn all of the module's exports with a redundant prefix (these things
happen), you could do this:
use Mythical::Graphics::Module Renaming => [
gfxColor => '%color', # this imports a hash
gfxPen => 'pen',
gfxLine => 'line',
# ....
# etc
];
...lower-casing the names as well.
If you need to add clarifying prefixes that a sloppy module author has
neglected to provide in the exports (these things happen), you go the
other way around:
use Legendary::Graphics::Module Renaming [
Color => '%gfxColor',
Pen => 'gfxPen',
Line => 'gfxLine',
# ...
# etc
];
...also lower-casing the initial letters.
If you are confronted with a standard module that uses a slightly
non-standard naming convention (it happens), you can rectify the
situation:
use Data::Dumper Renaming => [ Dumper => 'dump' ];
Now you can say "print dump \ %some_hash" instead of "print Dumper ...";
CAVEATS
* As has been mentioned in section Operation, no cross-check is done
between renaming exports and normal exports that go on in the same
"use" statement. This means that a renaming import may later be
overwritten by a normal import without a clear indication. This
happens when one of the new names given in renaming coincides with
one of the original ones imported through normal import.
* "Exporter::Renaming" only affects modules that do standard
exporting, that is, modules that inherit their "import" method from
Exporter. Modules that use a different "import" method are
unaffected and don't understand renaming lists.
* Renaming doesn't affect the name c sees for a function. This
should come as no surprise, since normal export doesn't affect this
name either. It is always the (package-qualified) name the function
was originally compiled with.
BUGS
* The lack of a cross-check between renaming and normal imports is
regrettable, but unlikely to be fixed unless Renaming is made part
of Exporter. Except for the simplest cases, only Exporter can parse
an export list.
* Calls of "use Exporter::Renaming" and "no Exporter::Renaming" don't
nest. Instead of switching unconditionally, "no Renaming" should
only switch off the behavior if it was off in the corresponding call
to "use Exporter::Renaming". A future release may address this.
SEE ALSO
Exporter, Perl
AUTHOR
Anno Siegel,
ACKNOWLEDGEMENTS
Thanks to Avi Finkel (avi@finkel.org) and Simon Cozens
(simon@simon-cozens.org) for a discussion of this project on IRC. While
brief, their remarks helped me think about things the right way.
COPYRIGHT AND LICENSE
Copyright 2003 by Anno Siegel
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.